The present invention relates to an insert nut for a screw nut joint of the type which comprises a substantially rectangular block, of which the short side substantially corresponds to the width of the outer groove portion in a T-formed groove, which outer groove portion is delimited by side flanges in a profile or the like and which inner groove portion is expanded relative to the outer groove portion, whereby the long side of the insert nut substantially corresponds to the width of the inner groove portion, and which nut by rotation can be transversally positioned and be brought into contact with the underside of the side flanges of the groove.
Insert nuts and screw nut joints of the above-described type are prior known through for example U.S. Pat. No. 5,116,161 and FR 2132645. Both cases are related to so-called parallelogram nuts, which after insertion in the groove can be rotated to a transverse position and maintain in that transverse position during tightening of the screw. Often, the insert nut is hidden by the part in which the screw is arranged and it is difficult to know with certainty that the nut has reach its optimal locking position. During displacement of the nut along the groove, the screw can rotate, whereby the nut to a certain extent can be part of this rotation and be forced out of its locking position. A similar type of nut can also be found in EP 0 478 928, although the document focuses on the threads of the nut, which threads are partly incomplete so that the screw during tightening in the nut is cutting threading for a more reliable locking of the screw in the nut.
Further, the document U.S. Pat. No. 4,666,355 describes a device at an insert nut, which device can hold the nut in position when the screw is screwed into the nut, so that the nut does not lose its position in the groove. The design that is being described to solve this holding is complicated, especially regarding manufacturing, as it comprises several parts which are intended to cooperate with each other.
The object of the present invention is to provide an insert nut which nut during rotation of the screw is always brought into its optimal, transverse position. Another object of the invention is to provide an insert nut that maintains in its transverse position, even when the nut is displaced along the groove.
These objects have been solved in that the nut is designed with a substantially quadratic shoulder section, which is arranged concentric with the threaded hole of the nut, and with substantially the same width as the short side of the nut, which shoulder section is intended to cooperate with the side edges of the outer groove portion, and that the shoulder section is divided in the vertical direction in a lower quadratic portion and an upper quadratic portion designed with two diametrically opposed rounded corners.